There is known a hybrid vehicle provided with an engine and an electric motor functioning as a drive power source, and an automatic transmission which constitutes a part of a power transmitting path between the drive power source and drive wheels and which is placed in a selected one of a plurality of gear or speed positions with engagement of selected at least one of a plurality of coupling devices. A hybrid vehicle disclosed in JP-2014-223888A is an example of this type of hybrid vehicle. This document discloses a control apparatus configured to control the electric motor (second electric motor) for controlling an input torque transmitted to the automatic transmission during a shifting action of the automatic transmission, on the basis of an output torque of the engine and a torque transmitted through the coupling devices, such that an angular acceleration value of an input rotary member of the automatic transmission (angular acceleration value of the second electric motor) coincides with a target value.
By the way, upon switching of a running state of the hybrid vehicle from a power-on state to a power-off state, with an accelerator pedal being returned to its fully released or non-operated position during a shift-down action of the automatic transmission in the power-on state, a control apparatus for the hybrid vehicle implements a hydraulic control to lower an engaging hydraulic pressure of a releasing-side coupling device to be brought into its released state to perform the shift-down action of the automatic transmission. At this time, an input shaft of the automatic transmission receives a regenerative torque of the electric motor, as well as a friction torque of the engine, so that a large negative total torque is applied to the input shaft. This negative torque causes a drop of a rotating speed of the input shaft, and a reverse progress of the shift-down action, so that speed synchronization of the input shaft is delayed with respect to a rise of an engaging hydraulic pressure of an engaging-side coupling device to be brought into its engaged state to perform the shift-down action, whereby the engaging-side coupling device is abruptly brought into the engaged state prior to a moment of the speed synchronization, giving rise to a risk of generation of an engaging shock of the engaging-side coupling device.